Q: A few weeks ago my 2001 Saturn’s “check engine” light came on. A friend told me to tighten the gas cap and it would make the light turn off. I did. About two weeks later, the light went out. Was it ...

Every week, we take your questions about what is going on under the hood of your vehicle and pose them to a knowledgeable mechanic in the Greater Toronto Area. In today’s column, we learn about ...